Conventional aircraft engines, such as piston aircraft engines, typically require adjustment to the ratio of air to fuel, termed the air-fuel mixture, provided to the engines during operation. For example, during takeoff, a piston aircraft engine typically utilizes a rich air-fuel mixture where the air-fuel mixture is stoichiometric. For better fuel economy after takeoff when the aircraft reaches lower-power cruising conditions, the aircraft engine can utilize a leaner air-fuel mixture where the amount of air added to the air-fuel mixture is increased such that the air-fuel mixture is greater than stoichiometric.
In conventional piston aircraft engines, once the aircraft reaches a cruising speed, a pilot manually controls leaning of the air-fuel mixture in an attempt to optimize fuel economy. During operation the pilot visually monitors an exhaust gas temperature (EGT) gauge, maintains the aircraft's throttle in a fixed state, and adjusts a fuel control lever to control the amount of fuel delivered to the engine. Based upon an output from the EGT gauge, the pilot adjusts the fuel control lever to set the air-fuel mixture to a certain amount to allow the engine to operate at an efficient fuel economy. For example, as the pilot reduces the amount of fuel delivered to the engine, the pilot can observe an increase in the EGT as provided by the EGT gauge up to a certain range of EGT values. As the pilot further decreases the amount of fuel delivered to the engine, the pilot will typically observe a decrease in the EGT provided by the EGT gauge. Such a decrease in the EGT value indicates to the pilot that he has reduced the amount of fuel delivered to the engine past an amount that allows the engine to operate at an efficient fuel economy. Therefore, in order to maximize the efficiency of the aircraft engine, the pilot increases the amount of fuel delivered to the engine until the EGT gauge indicates an increase in the EGT up to the previously detected range of EGT values.